Frequently, especially for biological processes, gaseous substances have to be fed into liquid media. During such process the substance to be converted is at equilibrium between the two phases, which depends on the concentration of the respective substance in the gaseous phase. In many cases the concentrations of the gaseous substances are, however, that low that a sufficient conversion into the liquid phase is not or only insufficiently possible. This applies mostly to those cases where the solubility of the gas cannot be improved by increasing the pressure.